Dejected teacher going about with company of actors (8)
I believe the answer is:
downcast
'dejected' is the definition.
(similar in meaning)
'teacher going about with company of actors' is the wordplay.
'teacher' becomes 'don' (don can mean an academic - especially at Oxbridge).
'going about' means one lot of letters goes inside another.
'with' becomes 'w' (abbreviation).
'company of actors' becomes 'cast'.
'don' enclosing 'w' is 'down'.
'down'+'cast'='DOWNCAST'
(Other definitions for downcast that I've seen before include "Sad" , "disheartened" , "Low in spirits" , "Dejected and discouraged" , "directed towards ground" .)